If the Sun were not the strongest, the two sister-planets, Earth and Venus, would gradually approach each other and would graze one another like two dragon-flies roaming together through the fields of the sky. But fortunately for us, the omnipotent Sun soon resumes its rights, and everything is restored back to order. The years of Venus are shorter than ours. Their precise duration is 224 days 16 hours 49 minutes 8 seconds. We do not yet know the diurnal rotation, i.e. the length of its days. According to certain observations, this appears to be about 24 hours, while others indicate that this planet does not turn upon its axis at all, or rather, that its rotation is equal to its revolution and that it always turns the same side towards the Sun. It is extremely difficult to determine its rotation, for two reasons. Firstly, because its atmosphere is very dense and always full of clouds, so that it is impossible to make out its geography and to follow in the telescope the displacement of its surface details; this is so easily done in the case of Mars, whose atmosphere is always clear, and whose rotation is known with perfect accuracy, its period being 24 hours 37 minutes 22½ seconds. The second reason is the difficulty presented by the phases of Venus. The closer the planet approaches us in its orbit round the Sun, the more does its disc apparently grow in size and the less we see of its surface, because it at the same time passes between the Sun and us, so that its illuminated hemisphere, being naturally turned towards the Sun which illuminates it, is hidden from us. My personal observations lead me to believe that the period of rotation is about 24 hours. At the Juvisy observatory we have often observed and photographed snowy patches in the north and south, probably marking the extremes of an axis and therefore a rotation. This special point is not yet decided. It is quite possible that the days are very long there, or rather, that they last for ever--perpetual day on one side and perpetual night on the other side. That would make it a very singular world. On one side light, heat, and life; on the other, the icy coldness of death. Some might choose for their abode perpetual sunlight; others might prefer a night illuminated perhaps by electric light; yet others might prefer to dwell in the dawn or the twilight. Beautiful Venus would then have one hemisphere in perpetual night and one in perpetual day. How strange! How our worlds must differ in the form of their organisms and the nature of their inhabitants! * * * * *